From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id 4827E1381F3 for ; Wed, 25 Sep 2013 09:22:33 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 955E6E0D1C; Wed, 25 Sep 2013 09:22:27 +0000 (UTC) Received: from icp-osb-irony-out5.external.iinet.net.au (icp-osb-irony-out5.external.iinet.net.au [203.59.1.221]) by pigeon.gentoo.org (Postfix) with ESMTP id 0EDC3E0BAC for ; Wed, 25 Sep 2013 09:22:25 +0000 (UTC) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhIFAFaqQlJ8lFH5/2dsb2JhbABbgwe+VIJ7gR4WdIIlAQEFDiQBMhMRCw0LCQwKDwkDAgECAUUTCAEBiAG7co9YCgyEBwOJNo5GhjInix6DMS8 X-IronPort-AV: E=Sophos;i="4.90,977,1371052800"; d="scan'208";a="156070756" Received: from unknown (HELO moriah.localdomain) ([124.148.81.249]) by icp-osb-irony-out5.iinet.net.au with ESMTP; 25 Sep 2013 17:22:24 +0800 Received: from localhost (localhost [127.0.0.1]) by moriah.localdomain (Postfix) with ESMTP id DED9F4EEC5 for ; Wed, 25 Sep 2013 17:22:22 +0800 (WST) X-Virus-Scanned: amavisd-new at lan.localdomain Received: from moriah.localdomain ([127.0.0.1]) by localhost (moriah.lan.localdomain [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id r-ObfA-eP6vS for ; Wed, 25 Sep 2013 17:22:06 +0800 (WST) Received: from [192.168.44.3] (moriah [192.168.44.3]) by moriah.localdomain (Postfix) with ESMTP id 2F0C34E79C for ; Wed, 25 Sep 2013 17:22:06 +0800 (WST) Message-ID: <5242AB3E.1030505@iinet.net.au> Date: Wed, 25 Sep 2013 17:22:06 +0800 From: William Kenworthy User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130823 Thunderbird/17.0.8 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Btrfs: how to fix slow sequential write performance? References: <5242A4CF.7000902@marc-stuermer.de> In-Reply-To: <5242A4CF.7000902@marc-stuermer.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit X-Archives-Salt: 0ace29a6-97c1-49d1-8279-8314a7c0ef1d X-Archives-Hash: 00a2cacc5a73a738b8ee7adab70323bf On 25/09/13 16:54, Marc Stürmer wrote: > Greetings fellow Gentooistas, > > at the moment I am doing some testing and evaluating of Btrfs on my own > system. Why? Just because I can and I am curious about it. > > Because I am doing that for evaluation purpose please don't give advise > like "go ZFS" or something like that, thank you. > > Kernel is 3.10.7, the file system is on one hard drive only (SATA). > > And here comes my question: sequential write access seems to be slow as > hell, actually something around like 10 Mbyte/s according to dd's output. > > The same HDD performed under ext4 with around 90 Mbyte/s. > > Command is something like: dd if=/dev/zero of=file.img bs=1G count=150 > > Nothing else is running at the time of writing, no scrub/balance on the > file system or other process eating up much cpu time. > > Mount option is "relatime" only. So is this a well known issue only with > this kernel or generally with this file system at the moment? > > Are there any possible fixes to squeeze better performance out of it or > is this unlikely to happen so that I should better take that into > account of my evaluation and maybe dump it then? > > Thanks in advance. > How old is the fs? - I am ran into a major slowdown due to COW snapshot fragmentation (VMs on ceph using btrfs) - a known problem. Using that kernel is also giving me an eventual hard lockup if I try and do a recursive defrag (on another system), but the ssd on an apple air defraged fine. btrfs is also seems very sensitive to how full it is. Have you tried a btrfsck? - some errors seem to cause slowdowns as well. BillK